1. Field of the Invention
This invention relates to a computerized tomographic apparatus CT for utilizing a radiation source, e.g., an X-ray source or a radioisotope.
2. Description of the Prior Art
In a conventional computerized tomographic apparatus, (although only an X-ray CT apparatus will be described in the present specification, the present invention is not limited thereto) of the type described above, when X-ray tomographic images (to be referred to as "tomographic images" hereinafter) at desired imaginary slice planes of an object to be examined such as a patient are obtained, the patient is held stationary while an X-ray tube is rotated about the longitudinal axis of the patient in a vertical section which involves the slice plane, and is intermittently projected with X-rays. When the entire projection data from every direction of the slice plane has been acquired, image reconstruction is performed on the basis of the acquired data, and thus a tomographic image of the desired slice plane is displayed on a display device.
When a plurality of tomographic images for a plurality of different slice planes is obtained in the X-ray CT apparatus as described above, the operation of the X-ray tube must be once interrupted after acquiring the entire projection data upon rotation of the X-ray tube through 180.degree. or 360.degree. for the first slice plane. Then, the patient is moved along the longitudinal axis such that the X-ray tube is located at a vertical section which involves the second slice plane. Then, rotation of the X-ray tube and X-ray exposure must be performed for the second slice plane as described with reference to the first slice plane.
Accordingly, when a plurality of tomographic images is required for a plurality of slice planes in a conventional X-ray CT apparatus as described above, it takes a long time to diagnose one patient, and the operation efficiency of the apparatus is lowered. In such a conventional X-ray CT apparatus, when a plurality of tomographic images is obtained for different slice planes of a patient who has been administered an X-ray contrast medium, the physiological condition of the patient changes from the time of data acquisition for the first slice plane to the time of data acquisition for the second slice plane. Thus, a plurality of tomographic images of a patient under identical physiological conditions cannot be obtained.